READ: Evidence for Evolution
7. Embryological Evidence
Embryological Evidence
Some of the oldest evidence of evolution comes from embryology, the study of how organisms develop. An embryo is an animal or plant in its earliest stages of development, before it is born or hatched.
Centuries ago, people recognized that the embryos of many different species have similar appearances. The embryos of some species are even difficult to tell apart. Many of these animals do not differ much in appearance until they develop further. Many traits of one type of animal appear in the embryo of another type of animal. For example, fish embryos and human embryos both have gill slits. In fish they develop into gills, but in humans they disappear before birth.
The similarities between embryos suggests that these animals are related and have common ancestors. For example, humans did not evolve from chimpanzees. But the similarities between the embryos of both species may be due to our development from an ancestor we have in common with chimpanzees. As our common ancestor evolved, humans and chimpanzees diverged and developed different traits.
This drawing was made to show the similarities between the embryos of many species. Embryos of many different kinds of animals: mammals, birds, reptiles, fish, etc. look very similar.
This is a six week old human embryo. Notice the similarities between this embryo and those of the other animals in figure 3.
CK-12 Foundation, Biology. http://creativecommons.org/licenses/by-nc-sa/3.0/